I need to say, it's an good Idea, but, the feeding system is horrible, sorry, the belt is an disintegrating one, so there is no need to an chamber, and that one is a bit small for an fucking 40mm grenade.
Wouldn't that be GAU 30mm Gatling cannon. I believe the shells on that are the same as that of the grenade shell. THey come in two types Armour peircing and high explosives. Also I want to bring your attenstion there is a German WW2 artillery Railway Gun Gustav . It fires 30inch shell. No imagine a 30 inch Gatling cannon same as the 30mm used on the A-10 Warthog. I wonder what the size it will be .
wow! too big and too heavy for good mobility on the battlefield on foot and far too large munitons wastage at a fire rate of 500-1200.per minutes and semi automatic is better and lighter and less noticeable on the battlefield .. and the fire prätzison suffers not as hard hit by the high fire rate of the weapon
More-dakka style weapons are well-known for their psychological effects, which DOES justify the massive consumption of ammo if your country has sufficient resources to resupply them.
Here's a few examples that are inefficient by ammo-consumption-to-kill ratio, but horribly efficient at terrifying soldiers in their era: 1. Maxim machine gun (Changed warfare forever) 2. MG42 (You will NOT like to hear the sound of this thing unless you're on Hitler's side) 3. M134 Minigun (Greatest waste of ammo of the era... not so much when you take the Oh Crap reaction of your enemy into account)